The Netherlands has stepped up the monitoring of traffic crossing its frontiers, a government minister said on Monday, as countries across Europe move to tighten border controls in response to an unprecedented migration crisis.

The move follows a decision last September to deploy mobile border guard units along roads and railways lines to intercept migrants and separate them from asylum-seekers.

"Those measures helped, but we were still seeing a rising number of smugglers being arrested, and you are seeing more people coming from safe countries, who aren't eligible for asylum," state secretary Klaas Dijkhoff told reporters.

The Netherlands received 200,000 immigrants last year, which fueled a backlash against immigration in a country that was once known for the generosity of its open-borders policy. In the 1960s, a period of high growth, the country opened its borders to migrant workers from Turkey and Morocco.

By slowing traffic as it crossed the border, border police would be better able to pick out vehicles that needed closer attention, Dijkhoff said.

Smuggling suspicions

Last year, Dutch border police arrested 330 people on suspicion of people smuggling, 200 of them during mobile border checks.

The measures would mean that arrivals from safe countries and those who had made asylum applications in several countries could be told there was no point in going further, he said.

Safe countries are designated under European rules, meaning migrants from those countries cannot claim asylum on the grounds of war or the risk of oppression or torture.

The aim was not to reimpose border controls as Europe seeks a solution to the crisis, Dijkhoff said. "We want to reach a deal with Greece and Turkey to close the borders, but until that happens we will have to take our own measures."

The vast stream of migrants fleeing war and poverty in the Middle East has forced countries across the European Union to impose extraordinary protective measures, placing the bloc's passport-free Schengen zone under pressure.